ported box for a JL Audio 12w6 v2

im building a ported box for a JL Audio 12w6 v2
on JL's site... they recommend 1.5 ft^3 ported
using 3/4 mdf... there external measurements were= 26.25" x 14" x 13"
and the slot port dimension is 1.5" x 12.5" x 29"
any idea what this is tuned to???
and would i benefit from making the box a little larger or tuning it to a different frequency to get a little more SPL??
thanks